Epiphyll specialization for leaf and forest successional stages in a tropical lowland rainforest

Questions The importance of tropical rainforest gap dynamics in biodiversity maintenance is not fully understood, in particular for taxa other than trees and lianas. We used epiphylls on rainforest leaves to study the importance of leaf- and forest-scale succession in determining biodiversity patterns by characterizing community change with leaf age in gaps and closed-forest habitats. We asked: (1) Do epiphylls show specialization for leaf and forest successional stages? (2) Can early- and late-successional epiphyllous species be recognized at these two scales? (3) How do epiphyll presence, species richness, and cover change with leaf and forest successional stages? Location Barro Colorado Island, Panama. Method Data were collected from 420 leaves, in three age groups and at two heights on shrubs in gaps and closed forest. We calculated turnover and nestedness components of dissimilarity to evaluate the importance of species replacement or accumulation during leaf and forest succession. Using generalized linear mixed models we determined what factors explain epiphyll species occurrence, richness and cover. Results Closed forest contained more liverwort and lichen specialist species than gaps. Specialist species were identified for older leaves only. Dissimilarity between leaves within age groups was dominated by turnover within and between forest successional stages. Dissimilarity between leaf age groups, at the site level, was dominated by nestedness, i.e., species accumulation. Both in forest and gaps, epiphyll presence and cover increased with leaf age for all taxa except fungi, while species richness increased only for lichens. Conclusion Early and late forest successional stages both contribute to epiphyll species richness by harboring specialized species. Among leaf successional stages, young leaves contain a mere subset of the species found on older leaves. Epiphyll communities do not follow classic succession, in the sense of changes being driven by species replacement, but are characterized by species accumulation through time.